Heat treatment of electrolytically-deposited iron



'INVETOR Novmzm 'BfPIH'n BY ATTORNEY N. B. FILLING Fig. l.

Filed Aug. 22. 1922 HEAT TRETMENT 0F ELEGTROLYTICALLY.DEPOSITED IRON May 31, 1927.

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Patented May 31, l927.'

UNITED STATES PATENT OFFICE.

NORMAN B. FILLING, 0F WILKINSBURG. PENNSYLVANIA, ASSIGNOR TO WESTI-NG- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VANIA.

HEAT TREATMENT OF ELECTROLYTICAILY-DEPOSITED IRON.

Application filed August 22, 1922. Serial No. 583,468.

` This invention relates to the treatment ot electrolytically deposited iron, more particularly to the heat treatment thereof in order to adapt the same to a `wider range of uses. s

lt has been proposed to reclaim undersized or worn mechine parts by building up layers of electrolytically deposited iron on said parts, as such material is very adherent and may be readily applied to such elements.

However, it has been found that the deposited iron is generally very brittle and may he pulverized by hammering.

t is desirable that material so deposited be modified in order to increase its workability, at the same time causing the same to become tough, and be in various stages of hardness for various applications. lt is` therefore, among the objects of the present invention to so treat electrolytically deposited iron that it shall become softened andv toughened and shall lose its extreme brittleness.

ln practising my invention, I heat treat the ldeposited iron at varying temperatures, such that they induce in the iron various changes of hardness, grain structure and composition. l have found that heating or annealing the iron at a 'moderate temperature causes a very material increase in the hardness thereof,- accompanied by a decrease in brittleness. Upon further annealing, the hardness `generally decreases until, at about. 900A C., the material is completely softened. At the same time there occur changes in the crystalline structure of the iron which correspond to theI changes in hardness thereof. ln the acconfipanyingdrawing constituting a part hereofA Figure` 1 is a curve showing the change in hardness with temperature' t Fig. 2 is a diagrammatic representation of `the structural changes taking place during the heat treatment, and

"Fig 3 is a curve showing the evolution of hydrogen from the iron. during the heat treatment. T

The h'eating or annealing may be accomplished in 1 any desired inert atmosphere selected to prevent excessive oxidation of the' iron, since the' changes brought about by .treatin-gare effected without interference by the external Iatnfiosph'ere Even hydrogen may 15e-successfully employed therefor. At

the more moderate temperatures the oxidation incurred by heating in air results in only a surface discoloration.

l have annealed various samples of electrolytically deposited iron at various temperatures. from ordinary room temperatures up to as 'high as 950 C. The original hardness ot' the deposited iron is substantially u imftected by an annealing temperature up to about 200 C. At 300 C. the hardness of the sample being annealed is increased very materially, as shown in the curve of Fig. l. wherein an increase of over 70% in hardness is noted between 200 and 300 C. Anncaling the material at successively higher temeperatures results in a progressive softening from a maximum at 300 to practically complete softening at 800. A slight increase in hardness occurs immediately after the A, transformation at about 000 C.

During the annealing operation, the toughness of the material also undergoes a change. Annealing at various temperatures up to 300 C. results in general lessening of the brittleness of the material and a corresponding increase in the toughness thereof. At 30 the material shatters at a single hammer blow; at 200 it cracks into a number ot' pieces, whereas at 300 the material may be hammered and deformed in a satisfactory manner for all machine operations. Above 300 there is no apparent change in the toughness of the material.

As shown diagrammatically in Fig. 2, the electrolytically deposited iron in the annealed state is composed essentially of close, compact crystals of needle-like form. A low-temperature annealing causes a progressive change'in they structure of the iron, it being manifested at about 300 C. in an indistinctness in the outlines of the crystals. Between 300 and G00"y C. there is very little change in the crystal structure, but from this temperature on the crystals coalesce into large structures which are` no longer needle-like. At 900 there isa complete structural change, resulting in a transformation from the large, polygonal crystals to a similar structure having small grains and very closely resembling iron which has initially been fused.

Simultaneously with the changes above noted, I have found that there occurs a del i composition of the iron-hydrogen compoundA mhd which is formed in the electrolytie depositionof the iron. The hydrogen in electrolytie iron is not merely in the free state dissolved in the iron but appears to be in the form of a Well defined compound which may be decomposed by heat treatment. At a temperature as low as 90O the compound actieely decomposes and the maximum rate of decomposition occurs between 200. and 300 C. Complete evolution of hydrogen from the iron is not aecomplishedbcfore reaching the transformation point at 900- C,

My process of annealing electrolytically deposited iron results in several important changes -in the material which render it more 'l useful in Various technical applications. The iron maybe softened Acompletely or may be partially hardened and simultaneously toughened. For maximum hardness and toughness, an annealing temperature of about-300O C.is-util`ized, whereas, for complete and rapidsoftening it is necessary to anneal at the relatively high'teinperatures of 800- to 950 C. Simultaneously'with the Changes-in hardness and toughness there occur changes in the crystalline structure of the iron and decomposition of the hydrogeniron compound therein.

30 My inventionis of special utility in cases Where deposits are made upon machine parts, such as, for instance, large steel shafts and the like which become worn or are machined under size. In such instances the metal is electrolytically deposited on the shaft and the same subjected to the heat treatment at the temperature which will trive the material the desired properties for the application of the shaft. By such procedure I am enabled to procure a considerable saving in such machine parts at a very low cost for repair thereof with a high degree of elliciency of the repaired part in service.

'l claim as my invention:

l.. A method of treating eleclrolytically deposited iron which consists in heatingr said iron to temperatures between 250O C. and about T200' C. to cause a decrease in the brittlencss and an increase in the hardness thereof. c

2. A method of heat treating: electrolytically deposited. ironv which consists in heatilrgr the same to a temperature between 250"- and 400o C. to cause a decrease in the brittleness and an increase in the hardness thereof.

In testimony whereof, I 'have hereunto subscribed my name this 17th ,day of August 1922.

NORMAN n. FILLING. 

